For example, a system board unit is incorporated in a server computer. The system board unit includes a system board and related casing and fixture components. A plurality of LSI (Large-Scale Integration) packages and a plurality of memory boards (memory cards) are mounted on the system board. The respective memory boards are placed on the system board in an upright state. Airflow paths are provided between the respective memory boards. The convection of airflow along a surface of the system board removes heat from the memory boards, as well as other heat generating components. The air of increased temperature is emitted to the space outside the server computer. Accordingly, the memory boards and other heat generating components are cooled down.